The present invention generally relates to the field of conveying and further processing of flat articles and, more particularly, to the conveying and further processing of printed products. The present invention also concerns a method and a device for gathering flat articles and collating printed products.
In the printing field, a method for gathering or collating comprises forming stacks, each comprising a plurality of printed products. The printed products contained in each stack generally differ from one another, and usually all of the gathered stacks essentially contain the same printed products in substantially the same sequence. In dispatch station technique, for example, a multitude of finished printed products are gathered respectively into dispatch units which can then be welded into a foil. Additionally, in dispatch station technique different supplements are gathered and then inserted as an enclosure into a main product such as a newspaper. Both of the finished printed products noted above, as well as the supplements, may have very different formats and different thicknesses. Furthermore, it is becoming more common to process other flat articles, such as CDs or different varieties of sample packages, with the printed products. In the field of book printing, for each book to be bound, a plurality of signatures is gathered. Each signature comprises a plurality of the book""s pages, and all signatures usually have the same format. In the same manner, xe2x80x9cstacksxe2x80x9d can be produced that only comprise a single flat article.
According to the prior art, printed products are gathered or collated by conveying stacks being produced behind each other along a collating route past a plurality of feed stations, and by adding one printed product to each stack at every feed station. The stacks are conveyed along the collating route parallel to their flat expanse and lying in a horizontal or inclined position on a stack support, which is either conveyed along with the stack or else is stationary and extends in the conveying direction. The printed products to be added to the stacks being conveyed past the respective feed station are, in most cases, supplied and deposited on the stack in a direction perpendicular to the stack conveying direction. Instead of conveying the stacks parallel to the flat expanse of the printed products, it is also known to convey the stacks with each one lying on an inclined stack support that extends transversely to the direction of stack conveyance and, while being supported in the downward direction, the stack supports are conveyed along together with the stacks in production. The printed products to be added to these stacks are usually supplied in the stack conveying direction.
Stacks being conveyed parallel to the flat expanse of the stacked printed products or the stack support surfaces (parallel conveyance) are conveyed along the collating route substantially one behind the other and the distance between stacks along the collating route is essentially determined by the largest product formats to be processed. In the case of stack conveyance that is not parallel, but instead is substantially transverse to the flat expanse of the printed products or stack support surfaces (transverse conveyance), the stacks are arranged along the collating route substantially lying one behind the other, so that the distance from stack to stack in essence is determined by the greatest stack height or stack thickness to be anticipated. Because the stacks usually have a relatively small height or thickness in comparison with their width and length (flat expanse of the stacked products), this means that for an equivalent conveying capacity, parallel conveyance calls for a much higher speed than transverse conveyance.
The length of a collating route in each case is determined by the number of feed stations to be provided and by how much space each feed station requires along the collating route. Using parallel conveyance, it is possible with relatively simple layouts to arrange the feed stations such that the distance between two neighbouring feed stations is not much larger than the actual stack expanse in the conveying direction. Accordingly, in each conveying cycle a product can be added to the stack. In transverse stack conveyance, if this was also possible, collating routes could be significantly shorter than collating routes with parallel conveyance. Unfortunately, however, this is not possible according to the prior art. Therefore, very compact collating layouts comprise combinations of parallel and transverse conveying systems. Examples of such combinations are drum-shaped arrangements, in which stacks in production are conveyed transversely around the circumference of the drum, while parallel conveyance is simultaneously employed in an axial direction, which results in a spiral-shaped collating route. The same is achieved in linear layouts, in which the stacks in production are conveyed transversely together with V-shaped compartments and simultaneously are displaced in a parallel manner within the compartments, resulting in a route with a diagonal course.
One of the reasons that feed stations to collating routes with transverse conveyance require a relatively large space is that every printed product to be supplied must first be inserted between two successive stacks or stack supports before it can be positioned on one of the stacks. The smaller the distance between stack supports, the higher the accuracy must be in the insertion step. Usually the products are supplied from above, held at upper edges in a hanging position. They are then inserted between the stack supports while still hanging, and are then released while the held upper edges are still positioned above the stack support. This means that during insertion the leading edge is substantially unguided. For a product with a relatively small length from leading to trailing edge when compared to the height of the stack, the free fall after release is relatively long. This means that insertion is to be carried out relatively slowly and, therefore, requires several conveying cycles. Accordingly, feed stations along the collating route need to have a corresponding length. Thus, a system of this kind imposes tight limits on the variations in format of the printed products to be fed, and the absolute conveying speeds have an upper limit, particularly when the products to be fed are not very stable and may already be deformed by a low relative wind speed.
A collating system with a multitude of V-shaped compartments that a printed product is inserted into at every feed station from a hanging position and laid against the trailing wall of the compartment, is described in the publication CH-668245. The feed stations in this system are arranged one behind the other, with a distance between one another that is almost twenty times greater than the extent of the compartments in the conveying direction (i.e., there are approximately twenty conveying cycles between two successive feed stations.). In the publication EP-0857681, it is proposed to insert hanging products between L-shaped stack supports from one side and above, and to release them when their upper edge is laterally aligned with the stack support and is still positioned above it. In this manner, it is possible to arrange the feed stations along the collating route overlapping one another so that the distance between feed stations may be reduced, depending on the arrangement, resulting in very few conveying cycles. However, in this system the leading edges of the products are unguided during insertion so that the limitations regarding insertion speed and absolute conveying speed are the same as in the case of the insertion from above without a lateral component.
It is an object of the present invention to create a method and a device for gathering or collating flat articles that makes it possible not only to combine transverse conveyance along the gathering route with small distances between feed stations in conveying cycles, but also significantly expand the limits applicable up until now with respect to the processing of articles having different formats and with respect to conveying speed, even when processing not very stable articles. Accordingly, an object of the present invention is a method and device for gathering or collating in more compact layouts with higher piece per time unit capacities than was possible for gathering or collating according to prior art.
In accordance with the present invention, flat articles are added to the stacks between the stack supports while being held at their leading edges, and are released only when the inserted article is substantially aligned to the stack position with only a very small, unguided movement required for positioning the article on the stack or laying it against the stack support. Immediately preceding insertion and during insertion, the articles are moved in a direction comprising a component that is parallel to the direction of stack conveyance. The articles may be inserted into V-shaped compartments as mentioned above, with the lower edge of each article to be inserted being held by a holding element and the holding element, and is only deactivated when the held edge has essentially reached the floor of the compartment. The floor supports the released article for further conveyance. It is possible to feed the articles from the side or from below in substantially the same manner.
Held guidance of the leading edges during insertion between successive stacks produces significantly higher insertion accuracy than held guidance of the trailing edges. Therefore, insertion is rendered less dependent on the stability of the articles and insertion speed. The higher insertion accuracy also makes it possible to have the stack support surfaces follow one another more closely, which once again either enables the stack conveying speed to be reduced, or using the same stack conveying speed, the piece per time unit capacity to be increased. A further advantage resulting from held guidance of the leading edges between stack supports and from the insertion accuracy associated with it is that it becomes possible to add articles with different formats and thicknesses to the stacks without risking conflicts between them during insertion or during positioning on the stacks.
With regard to the device for inserting articles according invention, articles are held by their leading edge between stack supports. A stack conveying means with stack supports being conveyed behind each other and feed means with holding elements being conveyed one behind the other, are arranged such that the conveying path of the holding elements traverses the conveying path of the stack supports. This means that the two conveying operations are to be matched to one another such that in traversing, one holding element is moved between each two successive stack supports. Furthermore, control means are to be provided for deactivating the holding elements during the traversing, advantageously right at the end of traversing.
The conveying system with traversing conveying paths is implemented in such a known manner in that the stack supports are arranged on a first conveying organ (e.g., traction chain), the holding elements on a second one, the two conveying organs being independent of one another and arranged in planes parallel to one another. Stack supports and holding elements are arranged facing towards each other on the corresponding conveying organ in such a manner that at the crossing they pass through one another in a combing manner. It is also possible to provide more than two conveying organs in such a manner that the holding elements pass between two stack support parts at a distance from each other, or two holding element parts are conveyed on either side of the stack supports.